hook and eye vs holdfast

hook and eye and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
hook and eye	Yes	No	No	No
holdfast	Yes	No	No	No

As nouns, holdfast is a hypernym of hook and eye; that is, holdfast is a word with a broader meaning than hook and eye:

Other hypernyms of hook and eye include fastener, fastening, fixing.

hook and eye (noun)	holdfast (noun)
a kind of fastener used on clothing	restraint that attaches to something or holds something in place